A comprehensive library for parsing XML schemas and generating code based on them.

This project originated as a fork of xsd-parser-rs but has since evolved into a complete rewrite.

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Overview

This library is built around a staged transformation pipeline that converts XML schemas into Rust source code. Each stage handles a specific level of abstraction and produces a well-defined intermediate representation. This makes the library highly flexible, testable, and suitable for advanced customization or tooling.

Pipeline Stages

1. Parsing: The parsing stage is handled by the Parser type. It loads XML schemas from files or URLs and uses pluggable Resolvers to fetch and preprocess schema definitions. The result is captured in a Schemas model, which stores namespaces, prefixes, and the raw schema structure needed for further processing.

2. Interpreting:: Interpreting is carried out by the Interpreter. This stage analyzes the schema definitions stored in the Schemas model and converts them into normalized, abstract type descriptions. The resulting MetaTypes model encapsulates schema semantics such as complex types, enumerations, references, and groups in a language-agnostic form.

3. Optimizing: Optimization is performed by the Optimizer, which takes the MetaTypes and applies structural transformations. These include deduplication, simplification of unions, merging cardinalities, and resolving typedef aliases. The goal is to prepare the type graph for idiomatic translation into Rust while reducing complexity.

4. Generating: The generation step uses the Generator to transform the abstract types into Rust-specific type data. It produces the DataTypes model by attaching names, Rust derivations, trait support, and rendering metadata. These enriched types form the basis for later rendering while still preserving schema semantics.

5. Rendering: Rendering is handled by the Renderer, which converts DataTypes into structured Rust code organized in a Module. It uses the RenderStep trait to define individual rendering steps. Several built-in steps are available, including support for serde or quick-xml. Users can also add custom RenderStep implementations to extend or modify the output.

Data Models

• Schemas: This model is built by the Parser and contains the raw XML schema data, including namespaces, prefixes, and schema file content. It serves as the foundation for interpretation and supports multiple sources and resolver types.

• MetaTypes: Generated by the Interpreter, this model contains language-neutral type definitions. It includes data like complex types, references, enumerations, and groupings derived from schema structure. It is suitable for introspection, transformation, and optimization.

• DataTypes: Produced by the Generator, this model holds enriched Rust-specific type data. Each type includes metadata for layout, naming, derivations, and other traits required for rendering idiomatic Rust code. This is the core input for the rendering process.

• Module: The final model is produced by the Renderer. It wraps the Rust source code output into a structured format, ready for file output or consumption as token streams. Modules support nested submodules, file splitting, and embedded metadata for customization.

Features

This library provides the following features:

• Rust Code Generation: Convert any XML schema into Rust code.
• Layered Architecture: Add user-defined code to manipulate type information or generated code.
• User-Defined Types: Inject existing types into the generated code to reuse predefined structures.
• serde Support: Generate code for serialization and deserialization using serde with serde_xml or quick_xml as serializer/deserializer.
• quick_xml Support: Direct serialization/deserialization support using quick_xml, avoiding serde limitations and leveraging asynchronous features.

Changelog

Below you can find a short list of the most important changes for each released version.

Version 1.2

This release introduces a series of architectural improvements, enhanced flexibility in code generation, and broader schema compatibility.

• Refactored Pipeline Structure The internal code generation pipeline has been refactored to introduce a new Renderer step and an accompanying DataType model. This separation gives users more control over the rendering process, allows better extension points for customization, and prepares the architecture for further growth.

• Refactored Serde Support Support for serde has been moved into dedicated renderer steps. This makes it possible to support multiple versions of serde-based implementations, such as serde-xml-rs 0.7 and 0.8, without mixing code. Each renderer step now cleanly encapsulates the logic for one serialization backend.

• Implement Support for Unstructured Data Added support for xs:any and xs:anyAttribute by introducing an internal representation for unstructured XML data. This enables working with flexible or unknown schema elements and fixes a long-standing gap in schema coverage.

• Implement Support for BigInt and BigUint Schemas defining integer types without upper bounds can now be mapped to num::BigInt or num::BigUint, depending on context. This is useful when working with large numeric values.

• Improved Documentation Support XSD annotations (xs:documentation) are now parsed and included as Rust doc comments in the generated code, improving type-level visibility and usability.

• Different Bug Fixes and Improvements

  • Enum restrictions on text types are now correctly interpreted and rendered
  • Complex types in the XML Catalog schema are now rendered correctly
  • Introduced per-type derive settings for advanced customization
  • Various naming, escaping, and formatting issues were resolved across the pipeline.
  • Generated names of nested elements now uses the name of the parent element as prefix to prevent name collisions.

Version 1.1

• Implemented feature to generated boxed quick_xml deserializers to reduce stack usage during deserialization
• Improved naming of the generated types
• Implemented feature to split generated code into multiple module files
• Improved and implemented advanced examples
• General bug fixes and improvements

Version 1.0

• First official release of xsd-parser

Planned Features

• Schema-Based Validation: Generate validators directly from schemas to validate XML data during reading or writing.

License

This crate is licensed under the MIT License.